低温胁迫对灰飞虱种群生长发育与繁殖的影响

为了探讨低温在灰飞虱Laodelphax striatellus(Fallén)种群发生发展中的作用,本文以南京冬季的旬平均最低温为依据,设定出-6～2℃的低温,研究了用该低温处理3～4龄若虫不同时间后,灰飞虱的存活、生长与繁殖特性。结果表明,灰飞虱3～4龄若虫有较强的耐低温能力,-6～2℃的温度下,其半致迷和半致死时间分别为1.22和20.49d。低温抑制了若虫的生长发育,发育历期明显延长。低温处理后成虫的性比有所提高,并且短翅率显著增加。3～4龄若虫低温处理1～7d后羽化的成虫有产卵前期缩短、寿命延长的趋势,但对繁殖力没有显著影响,并且低温处理2d后的产卵量要稍高于没有处理的对照。由此可见,-6～2℃低温的短期胁迫对灰飞虱种群的发生发展不会产生抑制作用。     

Contrasting impacts of a native and an invasive exotic shrub on flood‐plain succession

Abstract. Question: How do Coriaria arborea, an N‐fixing native shrub, and Buddleja davidii, a non‐N‐fixing exotic shrub, affect N:P stoichiometry in plants and soils during early stages of primary succession on a flood‐plain? Location: Kowhai River Valley, northeast South Island, New Zealand. Methods: We measured soil and foliar nutrient concentrations, light levels, plant community composition and the above‐ground biomass of Coriaria and Buddleja in four successional stages: open, young, vigorous and mature. Results: Coriaria occurred at low density but dominated above‐ground biomass by the vigorous stage. Buddleja occurred at 5.3 ± 1.0 stems/m² in the young stage and reached a maximum biomass of 520–535 g.m^‐2 during the young and vigorous stages. Mineral soil N increased with above‐ground Coriaria biomass (r²= 0.45), but did not vary with Buddleja biomass. In contrast, soil P increased with Buddleja biomass (r²= 0.35), but not with Coriaria biomass. In early successional stages, 70–80% of the species present were exotic, but this declined to about 15% by the mature stage. Exotic plant species richness declined with increasing Coriaria biomass, but no other measures of diversity varied with either Coriaria or Buddleja biomass. Conclusion: These results demonstrate that Buddleja dominates early succession and accumulates P whereas Coriaria dominates later succession and accumulates N. A key ecosystem effect of the invasive exotic Buddleja is alteration of soil N:P stoichiometry.     

土壤干旱对黄土高原3个常见树种幼苗水分代谢及生长的影响

应用盆栽试验,在人工控制土壤水分条件下对黄土高原3个常见树种丁香(Syringa oblata)、杠柳(Perip-loca sepium)和连翘(Forsythia suspensa)幼苗的生长及水分生理代谢进行了研究.结果表明,随干旱胁迫程度加剧,各树种耗水量明显减少;不同树种单株耗水量差异明显,表现为:连翘>杠柳>丁香.3树种新生枝条生长和叶面积扩展速率明显受土壤含水量影响,均表现为适宜水分>中度干旱>严重干旱,且在同一胁迫水平下,连翘>杠柳>丁香.随干旱胁迫程度的加剧和干旱时间的延长,丁香、杠柳和连翘叶片的含水量、游离脯氨酸以及叶绿素含量均有不同程度的变化,连翘和杠柳的叶片含水量在3种水分条件下均明显高于丁香,杠柳叶片游离脯氨酸含量明显高于丁香和连翘,连翘体内脯氨酸含量最低,丁香和连翘的叶绿素a/b值随土壤含水量的减少逐渐降低,杠柳则表现出相反趋势.不同树种对土壤干旱和高温的响应机制不同,但它们都具有较强的抗旱能力,适应黄土高原干旱的自然条件.     

具有抗HIV活性的天花粉蛋白在大肠杆菌中的表达及纯化

目的:天花粉蛋白(TCS)有较强的抗HIV活性。利用基因工程技术在大肠杆菌中表达TCS并进行纯化。方法:从新鲜栝楼叶片中获取TCS基因组DNA,利用PCR技术扩增其全长基因,经BamHⅠ和EcoRⅠ双酶切后与原核表达载体pRSET-A连接,转化感受态E.coliDH5α,提取质粒进行酶切鉴定及测序;将所获阳性重组质粒转化感受态E.coliBL21(DE3)得到工程菌,经IPTG诱导表达后,对表达产物进行SDS-PAGE及Western印迹鉴定;用Ni-NTA柱对所获目的蛋白进行纯化。结果:获得了目的蛋白的可溶性高效表达,并通过了Western印迹鉴定。经Ni-NTA柱纯化后,得到大量均一的6His-TCS融合蛋白。结论:TCS在大肠杆菌中的表达与纯化,为通过基因工程方法研制具有抗HIV活性的药物奠定了基础。     

Lack of glyconeogenesis in pancreatic islets: expression of gluconeogenic enzyme genes in islets.

Studies were performed to obtain evidence for glyconeogenesis from pyruvate to the triose phosphates in pancreatic islets. Inability to show this evidence would be consistent with the fact that glyceraldehyde, but not pyruvate, is a potent insulin secretagogue. Synthesis of 14C-labelled glucose from 14C-labelled pyruvate could not be detected. Since this might have been due to lack of sensitivity required to measure 14C-glucose production in such a scarce tissue as islets, cDNA probes were used to estimate the relative expression of genes coding for gluconeogenic enzymes. Islets expressed pyruvate carboxylase mRNA, but even islets from rats which had been starved (a condition which induces phosphoenolpyruvate carboxykinase (PEPCK) in liver, kidney and adipose tissue) showed no PEPCK mRNA. This is consistent with our previous work showing the absence of PEPCK enzyme activity in islets. Therefore, islets can convert pyruvate to oxalacetate, but since they lack PEPCK, neither the beta nor alpha cell can convert oxalacetate to phosphoenolpyruvate and carry out glyconeogenesis. Pyruvate carboxylase mRNA was increased in islets that possessed the capacity for glucose-induced insulin release versus islets that lacked the capacity to respond to glucose, such as islets from fed rats (versus starved rats) and in islets cultured at a high concentration of glucose (versus at low glucose). Pyruvate carboxylase, therefore, must be involved in pyruvate metabolism and not glyconeogenesis in the pancreatic islet.     

Characterization of the copper(II) binding site in the pink copper binding protein CusF by electron paramagnetic resonance spectroscopy

Electron paramagnetic resonance (EPR) spectroscopy has been used to structurally characterize the copper-binding site in CusF protein from Escherichia coli. The EPR spectra indicate a single type II copper center with parameters typical for nitrogen and oxygen ligands (A~200 G, g~2.186, g~2.051). The pulsed EPR data show that one of the ligands to Cu²⁺ is an imidazole ring of a histidine residue. The remote amino nitrogen of this imidazole ring is readily observed by electron spin-echo envelope modulation spectroscopy, while the imino nitrogen that is directly coordinated to the Cu²⁺ ion is observed by pulsed electron–nuclear double resonance (ENDOR). In addition, the ENDOR spectra reveal the presence of one more nitrogen ligand that was assigned to be a deprotonated peptide nitrogen. Apart from the two nitrogen ligands, it has been established that there are two nearby hydroxyl protons, although whether these belong to a single equatorial water ligand or two equatorial hydroxide ligands is not known.

毛白杨悬浮细胞系的建立及再生植株的获得

以毛白杨基因型TC152无菌苗为材料,研究毛白杨悬浮细胞系建立与植株再生,结果表明,通过悬浮培养和固体培养两种方法诱导毛白杨悬浮细胞分化不定芽,最终获得无菌生根苗。愈伤组织在MS＋1.5mg·L-12,4-D＋30g·L-1蔗糖的液体培养基中振荡培养,12d可建立悬浮细胞系;悬浮细胞系继代培养基为MS＋0.8mg·L-12,4-D＋30g·L-1蔗糖,继代周期为7d,悬浮细胞在MS＋1.0mg·L-16-BA＋0.1mg·L-1NAA＋0.5～1.0mg·L-1ZT＋30g·L-1蔗糖培养基中悬浮培养,可分化大量不定芽,每个培养瓶中可得到40～50个芽,个别不定芽玻璃化;不定芽在1/2MS＋0.6mg·L-1IBA＋20g·L-1蔗糖＋5.5g·L-1琼脂培养基上可分化不定根。悬浮细胞通过固体平板培养增殖为愈伤组织块后,在MS＋1.0mg·L-16-BA＋0.1mg·L-1NAA＋1.0mg·L-1ZT＋30g·L-1蔗糖＋5g·L-1琼脂的固体培养基上,不定芽分化率可达到70.00%。     

Changes in body mass and feeding behaviour in male harbour seals, Phoca vitulina, in relation to female reproductive status

Loss of body mass has been used as an index of the cost of reproductive effort in mammals. We studied changes in body mass of male harbour seals, Phoca vitulina , during the breeding season on Sable Island, Nova Scotia, Canada. Individually marked subadult ( n = 21) and adult ( n = 22) males were captured at approximately six-day intervals throughout the breeding season. Adult males weighed an average of 108 kg ± 5·6 (S.E.) at initial capture, whereas subadults weighed an average of 76 ± 6·6 kg. The rate of mass loss by adult males did not differ from zero during the pre-mating period (i.e. the period without receptive females), but differed significantly from zero (-0·91 ± 0·007 kg/day) during the mating period (i.e. the period with receptive females). By contrast, the rate of mass change of subadults did not differ from zero in either period, indicating that food availability was unlikely to be responsible for the observed changes in adults. Adult males lost up to 24% of body mass during the breeding season. Examination of sera for the presence of chylomicrons (i.e. evidence of recent feeding) also suggested that adults stopped feeding during the mating period, while subadults did not. These results suggest that reproduction represents a significant energetic cost to adult male harbour seals.     

Radiation injury in mouse lung: dependence on oxygen levels in the inspired gas

The relationship between radiosensitivity and the partial pressure of oxygen (PO2) in the inspired gas has been established for radiation pneumonitis as a measure of lung damage following irradiation of the mouse thorax. The radiosensitivity at low PO2 (0-1 per cent) fitted the linear transformation of the Alper, Howard-Flanders relationship giving a K value for lung tissue of 1.35 per cent oxygen with an oxygen enhancement ratio, m, of 2.13. The radiosensitivity at higher PO2 (5-21 per cent) did not fit the Alper, Howard-Flanders relationship probably because the PO2 of the inspired gas was greater than the PO2 in the alveolus. At the low PO2 levels in the inspired gas, back diffusion of oxygen from blood into the alveolus may lead to errors in the estimated value of K. If the low value of m is due to this 'contaminating' oxygen from blood then by taking a higher value for m, the amount of contaminating oxygen can be calculated (0.23 per cent) and a 'true' value for K(1.1 per cent) determined. Other uncertainties in this estimate of K due to the radiolytic consumption of oxygen and possible inadequacies in equilibration are discussed. Allowing for the uncertainties, it is concluded that the K value for lung damage lies towards the upper end of the range of K values measured for cells in vitro.